Temperature compensating hydraulic jarring tool

ABSTRACT

A hydraulic jarring tool is provided that vents pressure slowly from the tool&#39;s internal operating fluid chamber to allow maximum filling of the tool prior to the tool&#39;s entering a well and to provide for operating fluid expansion with temperature increases. The jarring tool includes an outer member and an inner member telescopically arranged. Spline means between said outer member and said inner member transmit torque. A hammer and anvil system provide a jarring effect upon actuation of the tool. An operating fluid is maintained in an operating fluid chamber between the outer and inner members. Seal means between the outer and inner members provides a fluid seal to contain the operating fluid. The seal means includes a seal and thermal relief valve assembly mounted for axial travel between said inner member and said outer member with a passage extending therethrough. A thermal relief valve means in the passage provides pressure equalization. The thermal relief valve means provides a controlled flow of operating fluid from the operating fluid chamber to relieve excessive fluid pressure without undue loss of operating fluid.

TECHNICAL FIELD

The present invention relates in general to the art of earth boring andmore particularly to a rotary hydraulic jarring tool.

BACKGROUND OF THE INVENTION

During the drilling of an oil or gas well or the like, situations areencountered wherein a component of the drill string becomes lodged inthe borehole. It is, of course, necessary to dislodge this component ofthe drill string in order to continue the drilling operation. A rotaryjarring tool is positioned in the drill string to allow the striking ofblows to the drill string and the loosening of and dislodging of thestuck portion of the drill string. For example, rotary jarring tools areinstalled in fishing strings to enable the driller to strike heavyupward blows against an engaged fish to jar it loose from its stuckposition. Rotary jarring tools are included in drill strings duringtesting, coring and wash-over operations to act as safeguards and toprovide a system with which to loosen the drill string should it becomestuck. The rotary jarring tools include a restraining or detentmechanism which holds the telescopic elements of the jarring tool in aclosed position until sufficient upward pull is exerted to trip therestraining mechanism and allow the telescopic elements to rapidly moveto their extended position. The force of the upward pull stretches thedrill pipe. When the restraining mechanism trips, the upward surge ofthe drill pipe in returning to its normal length will allow a severeblow to be imparted to the drill string by the jarring tool. Hydraulicjarring tools utilize a hydraulic operating or working fluid and valvesystem to provide the tripping action.

The jarring tool's seal system includes upper and lower seal assemblieswith the working fluid located therebetween. During the drillingoperation, elevated temperatures are encountered which causes theworking fluid to build up internal pressure and to experience viscositychanges. The seal assemblies and other components of the jarring toolmust be protected against the internal pressure buildup caused byincreases in temperature. Although the seal assemblies areprelubricated, a portion of an individual seal assembly, particularlythe portion of the seal assembly exposed to the mud side of the tool,may lose this prelubrication because of wash-out during tool operationsdownhole.

DESCRIPTION OF PRIOR ART

In U.S. Pat. No. 2,989,132 to J. L. Downen, patented June 20, 1978, ahydraulic oil well jar is shown. FIG. 3 is an enlarged fragmentarysectional view taken on the line 3--3 of FIG. 1 and illustrates a liquidescape check valve of the invention which is provided in the annularfloating seal thereof.

In U.S. Pat. No. 3,209,843 to Derrel D. Webb, patented Oct. 5, 1965, ahydraulic jarring tool with relief valve is shown. A relief valve servesto prevent rupture of the packing means in the tool. The relief valvebleeds fluid from an internal chamber upon an increase in pressure insaid chamber beyond a predetermined limit due to an increase intemperature and/or seepage of fluid from the well into the chamber.Rupture of the packing means is prevented and normal operation of thetool is permitted. The relief valve includes a valve seat, a ball valvefor engaging said seat, a plug threadedly received in a vent passage, aplunger engaging the ball valve and a compression spring engaging theplunger and the plug. The pressure at which the ball valve will moveaway from the seat may be varied by adjustment of the plug.

In U.S. Pat. No. 3,898,815 to James W. Young, patented Aug. 12, 1975, apressure and volume compensating system for reciprocating oilfielddrilling tools is shown. The well tool includes an outer member and aninner member telescopically arranged. A spline means between the outermember and the inner member transmits torque. A spring means ispositioned between the outer member and the inner member. A first sealmeans provides a fluid seal between the outer member and the innermember. A second seal means spaced from the first seal means provides afluid seal between the outer member and the inner member. At least oneof the seal means can move axially between the outer member and theinner member. The axial movement of the seal means accomplishes at leasttwo functions. The first function is that as the external pressureincreases, the seal means can move inwardly to compress any trapped airto the point that a pressure balance is maintained at all times. Thesecond function is to accommodate variations in volume created by thedrive mandrel as it moves axially within the tool housing.

SUMMARY OF THE INVENTION

The present invention provides compensation for pressure differentialbetween the pressure of the working fluid in a jarring tool and thepressure of the borehole fluid surrounding the jarring tool. The jarringtool includes an outer member and an inner member telescopicallyarranged. Spline means between the outer member and the inner membertransmit torque between the two members. The working fluid is retainedinside of the jarring tool by first and second seal means. An internalthermal relief valve vents pressure slowly from the jarring tool'sinternal chamber to allow maximum filling of the tool prior to itsentering the borehole, minimum tool size by limiting seal assemblytravel and compensation for working fluid expansion and viscosity changewith temperature increases. The thermal relief valve bleeds internalpressure slowly but is insensitive to pressure changes during boreholeoperations. The arrangement of the seal means and thermal relief valvelubricates the portions of the seal body which otherwise is unlubricateddue to loss of lubricant from wash-out during tool operation downhole.The above and other objects and advantages of the present invention willbecome apparent from a consideration of the following detaileddescription of the invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view illustrating an embodiment of a jarringtool constructed in accordance with the present invention.

FIG. 2 is an enlarged view of a portion of the jarring tool shown inFIG. 1.

FIG. 3 is an enlarged view of the thermal relief valve assembly includedin the jarring tool shown in FIGS. 1 and 2.

FIG. 4 is a schematic flow diagram illustrating the flow pattern of theoperating fluid in the jarring tool of FIGS. 1, 2 and 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and in particular to FIG. 1, a hydraulicjarring tool is illustrated therein and generally designated by thereference number 10. Only the right half of the jarring tool 10 isshown, however, it is to be understood that the jarring tool 10 issubstantially symmetrical. The jarring tool 10 is an impact tool adaptedto be positioned between the lower section of the drill string (notshown) and the upper section of the drill string (not shown) connectedwith the drilling equipment at the surface. The jarring tool 10 is thetype of tool generally called a hydraulic jar.

The hydraulic jar 10 comprises a telescopically arranged inner (upper)mandrel 11 and outer (lower) mandrel 27. The inner mandrel 11 actuallycomprises two cylindrical, hollow sections, namely the box and splinemandrel section 28 and the piston and wash pipe mandrel section 29. Thebox connection 30 is provided with an internal thread to be connected toan external thread on the pin end of the drill string component above.The outer mandrel 27 actually comprises four sections, namely the splinemandrel section 31, seal mandrel section 32, piston mandrel section 33and pin mandrel section 34.

The spline system of the jar 10 comprises spline 14 having radiallyinwardly directed splines on the inside diameter of the outer splinemandrel section 31 engageable with radially outwardly direct splines onthe outside diameter of the inner box and spline mandrel section 28. Thespline 14 provides a system for transmitting torque and providingtelescoping movement of the inner mandrel 11 and outer mandrel 27. Ajarring effect is provided by contact between the hammer 16 and anvil 15when the jar 10 expands and by contact between the hammer 17 and anvil18 when the jar 10 contracts. The bearing 19 improves axial movement ofmandrels 11 and 27. The wipers 12 and 26 restrict the entry of foreignmaterials into the working parts of the jar 10.

An annular hydraulic working or operating fluid chamber 21 is providedbetween inner (upper) mandrel 11 and outer (lower) mandrel 27. Anannular sliding sleeve valve or actuation means 22 is disposed in thehydraulic working chamber 21. The sleeve valve 22 is mounted for limitedlongitudinal movement in chamber 21 and forms a seal between thecylindrical surfaces of the inner and outer mandrels 11 and 27. Anannular lower stop member 23 is located below the sleeve valve 22 in theworking chamber 21. The sleeve valve 22 acts as a detent or restrainingmechanism providing for the slow metering of hydraulic working fluidfrom the upper chamber portion above the sleeve valve 22 to the lowerchamber portion below when the inner mandrel 11 is pulled upwardlyrelative to the outer mandrel 27 by tensioning the drill string. Thefluid is directed through passages in the sleeve valve 22 and thesurface of stop member 23. A release section 9 of working fluid chamber21 is located above sleeve valve 22. When the sleeve valve 22 comesadjacent release section 9 of the chamber 21, the wall friction isreduced. The working fluid still remaining in compression in chamber 21will be dumped around the sleeve valve 22 and behind the sleeve valve 22thereby drastically reducing the resistance of working fluid andpermitting upward strain on inner mandrel 11 to bring the hammer 16 andanvil 15 into jarring impact.

The lower portion of the working fluid chamber 12 is sealed by acompensator piston type seal and thermal relief valve assembly 24. Thelower seal and thermal relief valve assembly 24 comprises a floatingtemperature and pressure compensating annular seal between the outermandrel 27 and the washpipe section 25 of the inner mandrel 11. Aninternal thermal relief valve in assembly 24 vents pressure slowly fromthe working fluid chamber 21 to allow maximum filling of the jarringtool 10 prior to the tool's entering a well, minimum tool size bylimiting seal piston travel and providing for working fluid expansionwith temperature increases. The thermal relief valve bleeds internalpressure slowly and is insensitive to pressure changes during boreholeoperations. The seal and valve assembly system 24 lubricates theportions of the metal bodies which would otherwise be unlubricated dueto loss of lubricant by wash-out during tool operations downhole.

Referring now to FIG. 2, an enlarged view of the seal and thermal reliefvalve assembly 24 is shown. The assembly 24 includes an annular metalseal body 37 positioned between the inner mandrel 11 and the outermandrel 27. A series of elastomer seal elements 38 and 39 are positionedin grooves in the metal body 37. The seal and valve assembly 24 canslide axially along the working chamber area 21 to compensate for volumechanges created by the telescopic movement of the mandrels 11 and 27 andphysical characteristic changes of the working fluid caused bytemperature, pressure, etc. A bore 35 extends into the metal body 37from the working fluid side of the assembly 24. An internal thermalrelief valve 36 is positioned in the bore 35. A second bore 40 isconnected to the bore 35 and extends radially through the metal sealbody 37. The thermal relief valve 36 allows one-way flow of workingfluid from within the tool 10 outward but blocks flow in the reversedirection. The valve 36 bleeds internal pressure slowly but isinsensitive to pressure changes during the jarring tool's operation.This allows maximum filling of the jarring tool 10 prior to the tool'sentering a well. It also reduces tool size by shortening the length ofseal piston travel required. The valve 36 allows compensation forlubricant expansion with temperature increases without requiring agreater length of tool.

The seal and thermal relief valve assembly 24 also provides a continuinglubrication system for the metal bodies 11, 27 and 37. The upper seals38 act as lip seals and provides a more positive seal preventing flow ofworking fluid downward. The lower seals 39 also act as lip seals andprovide a more positive seal preventing flow of fluid upward. Thepassages 35 and 40 allow the working fluid passing through valve 36 tobe directed to the area between the upper seals 38 and lower seals 39.This provides lubrication to the portions of the metal body 37 andmandrels 11 and 27 which otherwise might be unlubricated due to loss ofprelubrication. Although the seal assembly 24 is prelubricated at thetime of the original construction of the jarring tool 10, thisprelubrication may be lost by wash-out during tool operations.

Referring now to FIG. 4, an illustration of the thermal relief valve 36is shown. This type of valve is commercially available, for example, athermal relief insert may be purchased from The Lee Company, 2225 EastRandol Mill Road, Arlington, Texas. A series of restrictor orifices 42in the thermal relief valve create turbulent flow prior to the fluidsexit through check valve 43. A filter 41 is located ahead of theorifices. The thermal relief valve 36 allows a small flow of operatingfluid out of the system when hermal expansion pressures substantially inexcess of normal pressures are developed. The expansion pressure isrelieved to the area between the seals 38 and 39. Relieving the pressureminimizes bowing or burst of components of the tool due to highpressure.

The structural details of one embodiment of a jarring tool 10constructed in accordance with the present invention having beendescribed, the operation of the jarring tool 10 will now be consideredwith reference to the flow diagram shown in FIG. 4 and to the elementsof the drawings shown in FIGS. 1-3. A lower drill string section orborehole tool is attached to the end of lower mandrel 27 at the threadedpin. The box connection on upper mandrel 11 is attached to the uppersection of the drill string. The working or operating fluid fills theworking chamber 21. The jarring tool 10 and drill string are loweredinto the borehole and the borehole operations continue. If a section ofthe lower drill string or borehole tool becomes tightly wedged in theborehole, a jarring action may be applied through the jarring tool 10 toattempt to dislodge the stuck portion.

The jarring tool 10 is initially in a fully contracted condition. Anaxial force is applied to the inner mandrel 11 through the drill string.This puts the working fluid into compression. The only way to relievethe internal pressure in the working fluid is through the sleeve valve22. A small portion of working fluid will pass through the sleeve valve22 into that portion of working fluid chamber 21, which is betweensleeve valve 22 and the seal and valve assembly 24. The sleeve valve 22will rise, relatively, in working fluid chamber 21 at an extremely slowspeed. When the sleeve valve 22 comes adjacent release section 9 of thechamber 21, the wall friction is reduced. The working fluid stillremaining in compression in chamber 21 will be dumped around the sleevevalve 22 and behind the sleeve valve 22 thereby drastically reducing theresistance of working fluid and permitting the upward strain to bringthe hammer 16 and anvil 15 into a jarring impact. The jarring effect istransmitted through outer mandrel 27 to the stuck portion which mightthen be dislodged. To reset the jarring tool 10, it is only necessary toallow the weight of the drill string above to be set down on the jarringtool 10. Working fluid travels into the portion of working chamber 21located above sleeve valve 22. Once the contraction is fully complete,the jarring tool 10 is ready to deliver another blow when required.

During the jarring tool's operation, the seal and thermal relief valveassembly 24 tend to float toward the bottom end of the tool. At jarring,it will occilate back and forth. Under some circumstances, the assembly24 will bottom out. Should the tool 10 encounter elevated temperatureswith the assembly 24 bottomed out, dangerously high pressure could beproduced in the working fluid. The thermal reliif valve 36 will allow asmall flow of operating fluid out of the system when thermal expansionpressures substantially in excess of normal pressures are developed.Since the viscosity of the operating fluid changes with temperature,controlled flow is important to prevent loss of excessive amounts ofoperating fluid. The pressure will be relieved by flow through screen41, orifices 42, and one-way valve 43 to the area between the seals 38and 39.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A hydraulic jarringtool, comprising:an outer member; an inner member, said outer member andsaid inner member being telescopically arranged; spline means betweensaid outer member and said inner member for transmitting torque; ananvil and hammer means for providing a jarring effect; an operatingfluid chamber between said inner member and said outer member containingoperating fluid; detent means for actuating said anvil and hammer means;and seal means between said outer member and said inner member forproviding a fluid seal to contain said operating fluid, said seal meansincluding a seal and thermal relief valve assembly mounted for axialtravel between said inner member and said outer member, said assemblycomprising an annular seal body with a pair of inner seal rings mountedbetween said inner member and said annular seal body defining an innerchamber and a pair of outer seal rings mounted between said annular sealbody and said outer member defining an outer chamber with a passagemeans extending from said operating fluid chamber to said inner chamberand said outer chamber and thermal relief valve means in said passagemeans for providing pressure equalization, said thermal relief valvemeans actuated at a preselected pressure and operating to allow limitedflow of operating fluid out of said operating fluid chamber into saidinner chamber and outer chamber and blocking flow into said operatingfluid chamber.
 2. A hydraulic jarring tool, comprising:an outer member;an inner member, said outer member and said inner member beingtelescopically arranged; spline means between said outer member and saidinner member for transmitting torque; an anvil and hammer means forpoviding a jarring effect; an operating fluid between said inner memberand said outer member; detent means for actuating said anvil and hammermeans; a first seal element between said outer member and said innermember for providing a fluid seal to contain said operating fluid; asecond seal element between said outer member and said inner member forproviding a fluid seal to contain said operating fluid, said second sealelement including an annular seal body mounted for axial travel betweensaid inner member and said outer member with a pair of inner seal ringsmounted on said annular seal body between said inner member and saidannular seal body and a pair of outer seal rings mounted on said annularseal body between said annular seal body and said outer member, saidpair of inner seal rings defining an inner chamber and said pair ofouter seal rings defining an outer chamber; passage means extendingthrough said annular seal body from a position proximate said operatingfluid to said inner chamber and said outer chamber; and thermal reliefvalve means in said passage means for providing pressure equalization,said thermal relief valve means actuated at a preselected pressure andoperating to allow flow of operating fluid out of said jarring tool intosaid inner chamber and said outer chamber and blocking flow back intosaid jarring tool.